Car2Go is, basically, a Zipcar competitor. Like Zipcar you get an RFID card that provides access. Just walk up, tap it on the windshield, and the car unlocks. Right now you find the keys hiding in the glove box and, after punching in a PIN and accepting a few terms and conditions on the car's center-mounted touchscreen, you're ready to roll. But, there are some differences between the services, like no annual fee with Car2go, offset by a higher one-time registration, $35 vs. $25 for Zip, and a potentially higher hourly fee as well, at $12.99 maximum per hour vs. $8.50 (though Zip's fee does go up to $13.25 on weekends).
But those fees are potentially much lower, too. Car2go actually charges by the minute, $.35 each, and interestingly the average user keeps a car for just 30 to 40 minute at a shot. 150 miles are included, plenty to get in and around the 52 square mile coverage area, but if you feel like roaming you can go well outside of that area too. You will, however, need to return the car back inside of it if you want the clock to stop running on your rental.
And that leads to one of the big changes with Car2go versus the others: you can park anywhere you like. Well, anywhere that's legal, anyway. Car location is updated via GPS and monitored centrally, along with information like fuel level and plenty of other metrics, all uploaded over an integrated data connection. It's T-Mobile. Using that connection you can also request that the car get a cleaning before it's rented again, and even call their support center -- hands-free, of course.
Location info is available through the company's apps, which sadly at this point are only available for iOS devices -- though there is a simple XML-based API if you feel like rolling your own. From here you can see where any of the 210 Fortwos are scattered about, or at least any of the available ones. The app is layered over Google Maps and so you can get walking directions if you don't know your way around. You can also place a reservation up to 24 hours in advance, though that may have a slight negative impact on your reputation as someone bound by neither rules nor schedules. Also, those who are sticklers about spelling mistakes should not use the iPad version, nor look too closely at the above screen shot.
In practice the process is easy enough, though it's the cars that may leave some wishing for a bit more. If you've never been in a Fortwo they are perhaps a bit more comfortable than you might have expected, but they're certainly no larger than you'd hoped. There's plenty of storage in the back for a messenger bag and a jacket but not much more. You could certainly stuff a couple loads of laundry in there if you don't care about how wrinkled they'd get on the way home, but making a run to Ikea to pick up a new and exotically named home entertainment center is definitely not in the cards.
Still, it's a great little car for short intra-city missions, and the service is structured to match that. The biggest problem is, of course, availability, and 210 cars in one American city (there are two more in Germany) are hardly going to revolutionize modern transportation. The company promises us that "a couple" of new cities are coming "within the next year" and, while that's too vague for our tastes, it's certainly a lot better than "nowhere" and "never."
Update: A couple commenters noted that there's an Android app called Find2Car that works well in Germany, but as of now is not available for booking cars based in Austin.